The present invention relates to a method of removing oil from oil contaminated material. This invention also relates to a method of removing chloride from the oil contaminated material after the oil has been removed. The present invention also relates to an apparatus designed for this purpose.
The present invention is a treatment method best described as a chemically induced hydrocarbon extraction process for the removal of oil from oil contaminated material. For example, oil contaminated well bore cuttings are created when oil based drilling fluid (mud) is utilized in the drilling process during oil exploration. The drilling fluid (drilling mud) is injected into the bore hole during the drilling process for the purposes of lubrication, cooling, controlling sub-surface pressure to prevent blowouts, stabilization and to assist in the removal of cuttings from the hole. The combination of drilling fluid (mud) and soil is brought to the surface where the oil based drilling mud is separated from the well bore cuttings and the oil based mud reused. During the separation process a considerable amount of fines are introduced into the drilling mud portion. This drilling mud can be reused until the concentration of solids exceeds in most cases 15 to 16 percent, at which time the mud has to be reworked. The resulting well bore cuttings containing unwanted oil are considered hazardous waste and present a large environmental problem during disposal as well as the safety hazards associated with handling combustible material.
Various technologies have been offered in an attempt to safely, efficiently and cost effectively remove the oil from well bore cuttings such as: incineration, thermal desorption (indirect fired), dirt burning (direct fired), screening and centrifugation, deep well injection, water based solvent washing solutions, and land farming. Incineration, thermal desorption, dirt burning are expensive as well as dangerous due to the real potential for explosion. Screening and centrifugation has proved to be ineffective as these methods are only capable of reducing oil concentrations to 10 to 15% by weight and the regulatory agencies, for example in the North Atlantic, are requiring less than 1% by weight remaining in the well bore cuttings before. discharge overboard in offshore oil drilling. Deep well injection is expensive and a questionable environmental solution. Water based solvent washing solutions appear to be effective in treating well bore cuttings where water based drilling fluids are used but not when oil based drilling fluids are used. This process is expensive and creates a need for water treatment. Land farming is expensive and takes a number of years to complete the process.
The trend in the industry is to lower discharge limits for hydrocarbon contaminated well bore cuttings. This has already been realized in the North Sea and in the Gulf Of Mexico. In the North Atlantic for example, the regulations are currently at the 15% hydrocarbon discharge criteria. The level will be reduced to 1% by weight in the near future.
This invention also provides a method for the reduction of chlorides in the well bore cuttings that are generated during land based drilling or exploration which commonly reach concentration in excess of 18000 ppm. The two most important criteria that have to be met when looking at landfill well bore cuttings in, for example, the province of Alberta, are reducing oil concentrations to less than 2.5% by weight and chlorides to less than 2500 ppm. When the oil based drilling fluid is constructed, calcium chloride or potassium chloride is commonly used for structural stabilization of the well bore hole.
There is thus a need in the industry to reduce the level of oil in oil contaminated material in the oil field. There is also a need to reduce the level of chlorides in land based drilling fields.
Thus, according to the present invention there is provided a method of removing oil from oil contaminated solids-containing material. This invention also relates to a method of removing chloride from the oil-depleted material, the oil contaminated solids-containing material after the oil has been removed. This invention also relates to an apparatus designed to accomplish the methods of the present invention.
In one embodiment of the present invention there is provided a process to extract oil from oil contaminated well bore cuttings so as to produce clean cuttings.
This invention further provides a quality of oil that can be reused in the construction of oil based drilling fluid or recycled for other purposes, such as fuel.
In a further embodiment of the present invention there is also provided a method to reduce chloride concentration to a level for safe land fill disposal during land based drilling operations. This can only be accomplished after the oil has been removed from the soil particles, which will then expose the more difficult to remove chlorides, that are attached to the soil particles that make up the well bore cuttings.
The removal of the contaminating oil in the well bore cuttings is accomplished by contacting the cuttings with a combination of surfactants in an oil carrier.
Thus according to one embodiment of the present invention there is provided a method of extracting oil from oil contaminated solids-containing material comprising:
mixing the oil contaminated solids-containing material with a combination of one or more surfactants in an oil carrier to provide a solids-containing treated material; and
subjecting the solids-containing treated material to one or more separating steps to extract oil therefrom and to provide an oil-depleted solids-containing material.
In a further embodiment of the present invention the method further comprises a step of removing the chloride from land based oil contaminated material.
In this embodiment there is provided a method of extracting oil and chloride from oil contaminated material comprising:
mixing the oil contaminated solids-containing material with a combination of one or more surfactants in an oil carrier to provide a solids-containing treated material;
subjecting the solids-containing treated material to one or more separating steps to extract oil therefrom and to provide an oil-depleted solids-containing material; and
treating the oil-depleted solid-containing material to reduce the concentration of chloride ions in the oil-depleted solid-containing material.
This invention also comprises an apparatus for achieving the methods of the present invention. In the embodiment of the present invention, which comprises the extraction of oil from oil contaminated material the apparatus comprises:
a means for mixing the oil contaminated solids-containing material with a surfactant-containing treating liquid to provide a solids-containing treated material; and
means for subjecting the treated materials to one or more separating steps to extract oil therefrom and provide an oil-depleted solid-containing material.
In the embodiment of the present invention which comprises the further step of separating the chloride from the treated material, the apparatus of the present invention further comprises:
a further mixing means;
a means to transport the oil-depleted material into the further mixing means;
a chemical input means for introducing a composition comprising one or more surfactants in a water carrier into the further mixing means; and
a separation means for separating the water carrier, which now includes chloride ions, from the further treated material.